Electric furnace



Sept 20 1932- T. B. BEcHTl-:L 1 1,878,619

ELECTRIC FURNACE Filed March 21. 1928 2 Sheets-Sheet 2 Patented Sept. 20, 1932 V; UNITED STATES 'rnaononn n. encarar.. or satan, on'ro nrnorarc ruim-Aca 4 'application-mea uma a1, 11328. serial no. 263,310.

AThis invention rela-testo electric furnaces. The electric furnace to which the invention applies in particular has helical heating resistors arranged within a heating chamber and supported. by refractory insulators' or supports,` I j `.l,Asfurnaceof'this character is ordinarily employed for the heat treatment of steel or other .metal upon whichoxid or scale. is formedwhen heated toa certain temperature. A partof the scale thus formed falls from thernetal into the furnace, and,.if allowed to .accumulate upon theresistor supports, it will seriously impair the efficiency of theresistors by restricting the dissipation ofzheat therefrom`lvl d` v i i :f

YIf the scale is conductive, an accumulation thereof vupon a resistor support will enable the current flowing through ahelical or yother v convoluted resistor carried by that support to Vbe short-circuited or pass direct from one turn ofthe resistor to an adjacent turn thereof, thereby causing the resistor to burn out within a relatively short time Aafter thescale has accumulated about the same.

The invention hasas an obj ect to provide an electric furnace whichhas high efciency and which is economical to operate.

Another object is to provide an electric furnace with an insulator or support which will. allow a helical or other tconvoluted resistor to dissipate its heat freely from substantially its entire radiatingsurface and which will prevent scale or other matter fro accumulating aboutthe resistor.

Another object is to provide anv electric furnace with refractory insulators or supports which are carried by the Wall thereof to support a helical or other convoluted resistor at several points intermediate its ends and which carry means for supporting the resistor intermediate adjacent insulators or supports.

Another object is to provide an electric furnace with helical or other convoluted resistors and supportsthereforwhich may be readily and easily removed and replaced.

AccordingT to the invention in one of its aspects, an electric furnace is provided with a resistor support having an open seat which is shaped longitudinally to retain a resistor therein and shaped transversely to provide a narrow supporting face and inclined faces sloping downward from the supporting face to zallow scale or other matter to fall freely from the support and thereby prevent it from accumulating upon theseat and about a re sistor arranged therein.

According to the Ainvention in another aspeet, an electric furnace is provided with resistor supports which are spaced from each other and carried by the furnace walls to support a resistor at spaced intervalsr along the same, a seat arranged upon each support and shaped to retain the'resistor therein andto 65 prevent accumulation of scale or other'matter about the resistor, and means carried by the supports for supportingwthe rcsi'stor intermediate 'a'dj acent resistorsupports,`

According to the invention in another a's- 70 peet, an electric furnace' is provided with ff resistor support to support a resistor` within t the 'furnace` a seat arranged upon the support and shaped to retain the resistor in position thereon and to4 permit the'free discharge of scale or other matter from around the rcsistor, and a bracket carried by a wall of the furnace and extending into the support to carry the same. v v

An electric furnace embodying the invention is illustrated in the accompanying drawings in'which theV views are as follows:

Fig. `1 is a vertical transverse sectio through the furnace;

Fig. 2fis a detail view of a resistor support 8.5 and a bracket for supporting the same;

Fig is a section on the line 3-3 of Fig. 2;

Fig. tis a detail view of another resistor support; t

Fig. 5 is a section on the line 5-5of Fig. 4;

Fig. 6 is a detail view showing a resistor supported throughout its length by means of intermediate supports carried by the supports shown in Fig. 4;

Fig. 7 is a plan view of the intermediate support shown in Fig. 6;

Fig. 8 is a section on the line 84-8 of Fig. 7; and

Fig. 9 is a view similar to Fig. 1 but shovv- 100 ing a different method of supporting the uppermost resistor.

Figs. 1 to a.

The furnace is provided with outer side walls 1, a roof 2, a bottom 3, and a linin 4, all of which constitute the walls of the urnace. p Y

Thelinin'g 4 isjmade of a refractory substance which is capable of withstanding high temperatures.

The side walls of thefurnaceare provided with a number of side brackets 5 which are embedded in the lining thereof and project in., ard into a heatingchamber 6 formed by the furnace walls. The brackets 5 are arranged 4in horizontal rows and each bracket is provided upon its upper edge with a convex seat 7 and upon its inward end with an upward flange or projection 8, both of which are arranged, in alinement with the correspondin seat-sand pro jections upon the other brac rets in thesame row. C The top wall of the furnace Icarries a number of angular roof brackets 9 which are arranged in rows longitudinally 'of the furnace and have the' vertical legs thereof extended Qfthroughthe roof 2 andlembedded in the linling 4 and the horizontal legs thereof arranged within the heating chamberV 6.

Each bracket 9.is provided at its `upper end with a pin 10 which bears upon the roof 2 to support the bracket, and uponA its horizontal leg with a convex seat y,1l andanend flange 12 which corresponds to the seat7 and the flange 8 of the bracket 5,. I l

The seats .11 and the flanges 12 are arranged in alinement with the corresponding seats and flanges on theother brackets in the 40 samerow. s 4 l j The brackets 5 and 9 are ordinarily4 made of a refractor metal, such as nichrome or other heat resisting substance. lEach of the brackets 5 and 9 carries a refractory insulator or resistor' supportl 13 which has an open slot 14 formed in the bottom thereof and shaped to conform to the seat and end flange upon the bracket, -j-as shown in Figs. 2 to 5. 5 0 The slot 14 enables the resistor support to be readily placed in position upon the' bracket and be removed therefrom, and the walls of the slot coact with the seat and end flange to position the insulator upon the bracket. Each resistor support 13 is provided with an open resistor seat 15 to support a helical or other convoluted resistor 16 which is shown as a wire or bar of resistance material wound into a helix.

The seat 15 is shaped to retain the resistor therein by being concave in longitudinal section, and to prevent the accumulation of scale about the same by being convex in transverse section. 65. The seat 15 is open at its top and has a very have the tops thereof arranged in alinement with the supporting surface of the seat 15 and which function as auxiliary or intermediate supports for supporting the resistor upon each side of its point of contact with the seat 15. y

. Each projection or rib 17 is shaped to permit the free discharge of scale from the seat 15 and to provide a narrow top with which the'resistor makes substantially a point or line contact. l v

A resistor support 13 lmay be placed upon the inward part of each bracket 5 and upon the lower part-of each bracket 9, and the seats 7 and 11. and the projections 8 and' 12 will positively position the supports in horizontal rows and-'aline each support with the other supports in the same row. 'i

Any one of the supports 13 maybe readily removed by simply lifting it from its bracket, and maybe as readily're'placed by simply inserting. Ianother support' upon the same bracket.

The. bottom of the furnace may valso be provided with resistor supports 13 which are spaced from each other and arranged in rows upon the lining of the furnace bottom.

A resistor 16 may then be placed in the seats`15 of the supports in'ea'ch row and supported thereby in a horizontal position. The resistor is then connected; into an electric circuit in the usual manner.

Any one of the resistors may be readily removed by simply Adisconnecting it from the electric circuit and then simply lifting it from the supports by which it is carried.

The furnace maybe provided witha hearth plate 18 which is made of suitable heat resisting material and supported from the bottom of the furnace by legs orposts 19.

Figs. to 8. i

The insulator or resistor support 2O shown in Figs. 4 and 5 is the sameas the support 13 except that the projections 17 are omitted from around the seat 15 and an angular pro-V jection 21 extends laterally from lthe lower part of each of its sides at each end' thereof.

The projections 21 upon each side of the support 20 are adapted to support one end of l the elongated intermediate support 22 shown in Figs. 7 and 8.

The intermediate support 22 has two side 130 bars 23 which are spaced apart and connected furnish a continuous support for a resistor 16, as shown in Fig. 6.

The lower lianges of the projections 2l support the ends of the side bars 23, and the vertical flanges of the projections 21 restrain the support 22 from lateral movement.

The tops of the side bars 23 and the crossbars 24 are shaped to permit scale to fall freely therefrom and thereby prevent an accumulation of scale about a resistor arranged thereon.

Fig. 9.

The uppermost resistor supports, instead of being carried by brackets 9, are shown in this figure as being carried' by cross-bars 25 which are made of refractory metal and have the ends thereof embedded in the lining of the side walls.

Each cross-bar 25 is provided at intervals along its length with projections 26 and seats 27 which are similar-to the projections 12 and seats 11 on the brackets 9.

Each seat 27 has a projection 26 arranged at each end thereof to retain a resistor support 13 or 20 thereon, in which position the resistor support is in alinement with the corresponding resistor supports carrled by `the other bars 25.

The invention herein set forth is susceptible of various modifications without departing from the scope thereof as hereinafter claimed.

The invention is hereby claimed as follows 1. An electric resistance furnace, comprising furnace walls forming a heating chamber, helical resistors arranged horizontally in l yhelical resistors arranged horizontally in resistor supports and having convex supporting surfaces to engage said resistors and supe port the same throughout the length thereof.

4 3. An electric resistance furnace, comprising furnace walls forming a heating chamber, brackets arranged in horizontal rows in said chamberand supported by said Walls, an insulator arranged upon each bracket and having an open seat concave in longitudinal section and convex in cross-section, and a helical resistor supported by each row ofbrackets and making substantially a line contact witheach seat therein.

'4. An electric resistance furnace, comprising furnacewalls forming `a heating chamber,

brackets arranged in horlzontal rows in saidchamber and supported by said walls, an insulator arranged upon each bracket and having an open seat concave in longitudinal section and convexin cross-section, intermediate supports carried by said insulators and having convex supporting surfaces, and helical resistors supported horizontally by said-seats and said intermediate supports.

5. A11 electricresistance furnace, comprising furnace walls forming a heating chamber, brackets arranged in horizontal rows in said chamber and supported by said walls, an insulator arranged upon each bracket and having an open seat concave in longitudinal section and convex in cross-section, intermediate supports extending between and carried by adjacent insulators and having convex supporting surfaces, and helical resistors arranged horizontally in said chamber and supported substantially throughout the lengths thereof by said vseats and said intermediate supports.

Y 6. The combination' with an electric resistance furnace, of aresistor support comprising a bracket for attachment to a wall of said furnace, a refractory insulator supported by said bracket and having a slot in the under side thereofto receive the same, and an open resistor seat formed on said insulator and 'shaped to retain a. helical resistor therein and to prevent accumulation of scale about the same. j j

7 lThe combination witlnan electric resistance furnace, of `a resistor support comprising a bracket for attachment to a wall of said furnace, a refractory insulator supported by said bracket and having a slot in the under side thereof to receive the same, an open resistor seat formed on said insulator and shaped to retain a helical resistor therein and to prevent accumulation of scale about the same, and means on said insulator to carry an intermediate support between adjacent resistor supports. 4 8. An electric resistance furnace, comprising furnace walls forming a heating chamber, helical resistors arranged horizontally in said chamber, refractory resistor supports carried by said furnace Walls to support said ber, y'helical resistorsv arranged horizontally in said chamber, refractory resistor supports carried by said furnace walls Vto support said resistors, an openl resistor seat formed on each support` and shaped longitudinally f to `retaina helical resistor therein and shaped transversely to' make substantially a line contact with said resistor, projections carried by said supports upon the sides thereof, and intermediate resistor supports carried by said projections.

- 10. Anelectric resistance furnace, comprising furnace walls formin a heating chamber,

brackets arranged in horizontal rows in said chamber and supported by said walls, an in-` sulator arranged upon each bracket and havingan open seat concave in longitudinal section and convex in cross-section, projections carried by said insulators upon sides thereof,

said seat, and means to support said insulator within said furnace apart from any other object to allow said scale to fall freely from said insulator.

In witness whereof, I have hereunto subscribedmy name.

' THEODORE B. BECHTEL.

intermediate supports carried by said pro jections and having convex supporting surfaces, and helical resistors sup orted horizontally by 'said seats and said intermediate supports.

11. An electric resistance furnace, comprising furnace Walls forming a heating chamber, helical resistors arranged in said chamber, brackets carried by said furnace walls, refractory resistor supports removably mounted upon said brackets to support said resistors, and an open resistor seat formed on each support and shaped longitudinally and transversely to provide point contact surfaces for said resistors.

12. The combination, with an electric resistance furnace having resistors arranged therein, of a support for said resistors comprising a refractory insulator having an open seat shaped longitudinally to retain a resistor therein and shaped transversely to rovide a narrow supporting face and sides sloping downwardly from said face to allow scale to fall freely from said insulator and thereby prevent the same from accumulating upon said seat, and means to support said insulator within said furnace.

13. The combination, with an electric resistance furnace having resistors arranged therein, of a support for said resistors coin-v prising a refractory insulator having an open seat substantially concave in longitudi- 'nal section to retain a resistor therein and 

